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Heat Transfer - Engineering

Q1:

In a heat exchanger with steam outside the tubes, a liquid gets heated to 45°C, when its flow velocity in the tubes is 2 m/s. If the flow velocity is reduced to 1 m/s, other things remaining the same, the temperature of the exit liquid will be

A less than 45°C

B more than 45°C

C equal to 45°C

D initially decreases and remains constant thereafter.

ANS:B - more than 45°C

In a heat exchanger, the temperature of the exit liquid depends on various factors including the flow velocity, the heat transfer coefficient, and the temperature of the steam outside the tubes. When the flow velocity is reduced from 2 m/s to 1 m/s while other factors remain the same, the residence time of the liquid inside the heat exchanger increases. This means that the liquid spends more time in contact with the hot steam, allowing more heat transfer to occur. As a result, the temperature of the exit liquid will be higher than 45°C. Therefore, the correct answer is: more than 45°C.